Distributed load management on network devices

ABSTRACT

This disclosure relates to a system and method for dynamically managing load on network devices in a distributed manner. As the proliferation of data rich content and increasingly more capable mobile devices has continued, the amount of data communicated over mobile operator&#39;s networks has exponentially increased. Upgrading the existing network to accommodate increased data traffic is neither desirable nor practical. One way to accommodate increased data traffic is by utilizing network resources more efficiently. This disclosure provides systems and methods for efficiently utilizing network resources by dynamically configuring the network in a distributed manner based on real-time load information.

RELATED APPLICATIONS

This Application is a continuation (and claims the benefit of priorityunder 35 U.S.C. §120) of U.S. application Ser. No. 13/912,867, filedJun. 7, 2013, entitled “DISTRIBUTED LOAD MANAGEMENT ON NETWORK DEVICES,”Inventors Ramakumar Rajagopalan, et al., (now issued as U.S. Pat. No.9,294,981) which is a continuation (and claims the benefit of priorityunder 35 U.S.C. §120) of U.S. application Ser. No. 12/984,335, filedJan. 4, 2011, entitled “DISTRIBUTED LOAD MANAGEMENT ON NETWORK DEVICES”(now issued as U.S. Pat. No. 8,477,730). The disclosures of the priorapplications are considered part of (and are incorporated by referencein) the disclosure of this application.

FIELD OF THE DISCLOSURE

This disclosure relates generally to a system and method for dynamicallymanaging load on network devices in a distributed manner.

BACKGROUND

Wireless networks are telecommunications networks that use radio wavesto carry information from one node in the network to one or morereceiving nodes in the network. Cellular telephony is characterized bythe use of radio cells that provide radio coverage for a geographicarea, with multiple cells arranged to provide contiguous radio coverageover a larger area. Wired communication can also be used in portions ofa wireless network, such as between cells or access points.

Wireless communication technologies are used in connection with manyapplications, including, for example, satellite communications systems,portable digital assistants (PDAs), laptop computers, and mobile devices(e.g., cellular telephones, user equipment). Users of such applicationscan connect to a network (e.g., the Internet) as long as the user iswithin range of such a wireless communication technology. The range ofthe wireless communication technology can vary depending on thedeployment. A macro cell transceiver is typically used by serviceproviders to provide coverage over about a five kilometer distance. Apico cell transceiver can provide coverage over about a half kilometerdistance, and a femto cell transceiver can provide coverage over a50-200 meter distance. A femto cell transceiver is similar in coverageto a WiFi (WLAN) access point and can be used to provide network accessover a short range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-2 illustrate communication networks including a long termevolution (LTE) topology in accordance with some embodiments;

FIG. 3 is a block diagram of a communication system in accordance withcertain embodiments;

FIG. 4 is a call flow diagram of a distributed overload protectionprocedure in accordance with certain embodiments;

FIG. 5 is a block diagram illustrating offloading at a network device inaccordance with certain embodiments;

FIG. 6 is a call flow diagram of a distributed offloading procedure inaccordance with certain embodiments;

FIG. 7 illustrates the implementation of a network device in accordancewith some embodiments;

FIG. 8 illustrates a network device in accordance with certainembodiments.

FIG. 9 illustrates a logical view of the software architecture of anetwork device in accordance with certain embodiments.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

Certain embodiments disclose a system comprising a first network devicein communication with at least one second network device over acommunication channel, the first network device sending a message fromthe first network device to the second network device through thecommunication channel to request load information, and in response toreceiving the load information from the second network device, the firstnetwork device determining the amount of load to be handed over to thesecond network device, and the first network device sending a messagefrom the first network device to the second network device to requestsetting aside data transfer capacity for the first network device, andin response to receiving a confirmation from the second network devicethat the data transfer capacity has been set aside for the first networkdevice, the first network device selecting mobile stations to be handedover to the second network device, and the first network devicere-routing the selected mobile stations to the second network device bymodifying a serving network device identifier in a mobile stationidentifier.

Example Embodiments

The increase in mobile data traffic is straining operators' existingpacket core elements. The increase in data traffic can overload networkdevices, and it may even cause service disruptions that may necessitatemanual interventions by operators. Unfortunately, the demand for mobiledata is not expected to slow, especially as mobile devices become moresophisticated and as users become more dependent on mobile devices. Inorder to provide high quality services amid a rapid increase in datatraffic, operators often invest heavily on improving thetelecommunication infrastructure by, for instance, installing morenetwork devices. However, the heavy investment in infrastructure canrapidly increase the data delivery cost, and it can also challenge theprevalent flat-rate data service models. Furthermore, even the improvedinfrastructure cannot entirely eliminate service disruptions. If theimproved infrastructure is inefficiently managed, many critical issueswith large data volume will remain. Therefore, an efficient operation ofnetwork is important for delivering quality services. This disclosuredescribes systems and methods for efficiently utilizing networkresources by dynamically configuring the network in a distributed mannerbased on real-time load information.

At a high level, the goal of dynamic load management is to fully utilizenetwork resources using the real-time network usage information, i.e.,real-time load information. Dynamic load management can be beneficial onat least two fronts: network device overload prevention and data trafficoffloading. An overloaded network device cannot accept new attachrequests from mobile stations, nor can it provide high quality servicesto already attached mobile stations. This can lead to customerdissatisfaction as well as potential revenue losses for operators.Network device overloading often occurs when the volume of data trafficincreases. For instance, if a large number of users commute to the citycenter during rush hour, network devices near the city center can becomeprone to overloading due to the increased amount of data traffic. Inorder to address such worst-case data traffic, operators often choose toincrease the network capacity by installing more network devices, eventhough network devices in suburbs are severely under-utilized. Such adecision increases data delivery cost, which in turn reduces revenue foroperators. Operators could have prevented overloading simply bydynamically reconfiguring the network based on the real-time loadinformation such as the amount of load being handled by each networkdevice. For instance, operators could have monitored the amount of loadbeing handled by each network device and re-routed excessive datatraffic from over-utilized network devices to under-utilized networkdevices.

Dynamic load management can also address data traffic offloading.Sometimes, network devices are taken out-of-service for scheduledmaintenance or other activities. Before network devices are takenout-of-service, they need to offload or hand over all attached sessionsto other operating network devices. There are offloading standards,including Iu flex and Gb flex, that specify offloading procedures.However, these standards do not exploit real-time load information ofeach network device. Therefore, after offloading, the data load amongoperating network devices can become unbalanced. The unbalanced dataload can strain the network resources and can eventually overload othernetwork devices. The newly overloaded network devices will have tooffload their data traffic to other network devices, which can furtherreduce the number of operating network devices and induce even moresevere unbalance in the load distribution. Such a cascade effect mayeven lead to a network breakdown. Furthermore, existing offloadingprocedures can cause service disruptions to active users, leading tocustomer dissatisfaction. Dynamic data load management can address theseissues by monitoring real-time load in each network device in thenetwork and offloading data traffic to under-utilized network devices.

Although dynamic load management can be beneficial, implementing it in acomplex network can be challenging. Operators could introduce acentralized unit that gathers load information of all network devicesand distributes load to network devices. However, introducing a newcontrol unit in an already-complex network may require an extensivenetwork restructuring, which can be costly and undesirable. Furthermore,operation of the entire network becomes dependent on the centralizedcontrol unit. If the centralized control unit fails, the entire networkcan fail. A distributed solution described in this disclosurecircumvents these issues. In fact, an embodiment of the disclosedinvention is capable of operating on an existing network with minimalrestructuring, if at all.

FIG. 1 illustrates a communication network that includes a distributeddynamic load management mechanism in accordance with certainembodiments. FIG. 1 includes a number of radio access technologies suchas a 1×RTT transceiver 100, a high-rate packet data (HRPD) transceiver102, and an evolved high-rate packet data (eHRPD) transceiver 104, eachof which can connect to an access network 106. An evolved Node B(eNodeB) transceiver 108 is an LTE network radio network component thatconnects to an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)110. Other radio access technologies such as WiFi, Femto, WiMAX, or anyother radio spectrum technology can use transceiver 112 to connect tothe network using a broadband or other access network.

The access network 106 can communicate with an access gateway 116 thatimplements a combination of functionalities such as a packet dataserving node (PDSN), a HRPD serving gateway (HSGW), and a servinggateway (SGW). In operation, the PDSN functionality can be used with1×RTT 100, the HSGW functionality can be used with HRPD 102 and eHRPD104, and the SGW functionality can be used with the eNodeB 108. Theaccess gateway 116 can communicate with an anchor gateway 118, which canimplement a packet data network gateway (PGW) and a Home Agent (HA) anda mobility management entity (MME) 120. On the access network side, theanchor gateway 118 can also communicate with an evolved packet datagateway (ePDG) 122 which provides connectivity to the WiFi/Femto/othertransceiver 112. On the packet core side, the anchor gateway cancommunicate with the operator's IP service domain 124, the internet 126,and IP multimedia subsystem (IMS) 128. An authentication, authorization,and accounting (AAA) server/home subscriber server (HSS) 130 cancommunicate with the access gateway 116, the anchor gateway 118, orboth.

The Home Subscriber Server (HSS) 130 can be a master user database thatsupports IMS network entities that handle calls. The HSS 130 storessubscription-related information (subscriber profiles), performsauthentication and authorization of the user, and can provideinformation about the subscriber's location and IP information. The AAAserver 130 can provide authentication, access control, and accounting tothe network. The authentication can involve verification of thesubscriber, the access control can involve granting or denying access tospecific services, and the accounting that can take place is thetracking of the use of network resources by subscribers. Other servers,such as the Home Location Register (HLR) can be used in otherembodiments. In certain embodiments, the AAA/HSS 130 can communicatewith the access gateway 116 for charging purposes.

The LTE communication network includes a PDN gateway (PGW) 118, aserving gateway (SGW) 116, an E-UTRAN (evolved-UMTS terrestrial radioaccess network) 110, and a mobility management entity (MME) 120. Theevolved packet core (EPC) of an LTE communications network includes theMME 120, SGW 116 and PGW 118 components. In some embodiments, one ormore EPC components can be implemented on the same gateway or chassis asdescribed below.

The SGW sits in the user plane where it forwards and routes packets toand from the eNodeB and PGW. The SGW also serves as the local mobilityanchor for inter-eNodeB handover and mobility between 3GPP networks. TheSGW routes and forwards user data packets, while also acting as themobility anchor for the user plane during inter-eNB handovers and as theanchor for mobility between LTE and other 3GPP technologies (terminatingS4 interface and relaying the traffic between 2G/3G systems and PGW).For idle state UEs, the SGW terminates the down link data path andtriggers paging when down link data arrives for the UE. The SGW managesand stores UE contexts, e.g. parameters of the IP bearer service andnetwork internal routing information. The SGW also performs replicationof the user traffic in case of lawful interception.

The PGW acts as the interface between the LTE network and other packetdata networks, such as the Internet or SIP-based IMS networks (fixed andmobile). The PGW serves as the anchor point for intra-3GPP networkmobility, as well as mobility between 3GPP and non-3GPP networks. ThePGW acts as the Policy and Charging Enforcement Function (PCEF), whichmanages Quality of Service (QoS), online/offline flow-based chargingdata generation, deep-packet inspection, and lawful intercept. The PGWprovides connectivity to the UE to external packet data networks bybeing the point of exit and entry of traffic for the UE. A UE may havesimultaneous connectivity with more than one PGW for accessing multiplepacket data networks. The PGW performs policy enforcement, packetfiltering for each user, charging support, lawful interception, andpacket screening. The PGW also provides an anchor for mobility between3GPP and non-3GPP technologies such as WiMAX and 3GPP2 standards (CDMA1× and EVDO).

The MME resides in the EPC control plane and manages session states,authentication, paging, mobility with 3GPP 2G/3G nodes, roaming, andother bearer management functions. The MME can be a standalone elementor integrated with other EPC elements, including the SGW, PGW, andRelease 8 Serving GPRS Support Node (SGSN). The MME can also beintegrated with 2G/3G elements, such as the SGSN and GGSN. Thisintegration is the key to mobility and session management interworkingbetween 2G/3G and 4G mobile networks.

MME 120 is a control-node for the LTE access network. The MME isresponsible for UE tracking and paging procedures includingretransmissions. MME 120 handles the bearer activation/deactivationprocess and is also responsible for choosing the SGW for a UE at theinitial attach and at time of an intra-LTE handover. The MME alsoauthenticates the user by interacting with the HSS 130. The MME alsogenerates and allocates temporary identities to UEs and terminatesNetwork Access Server (NAS) signaling. The MME checks the authorizationof the UE to camp on the service provider's Public Land Mobile Network(PLMN) and enforces UE roaming restrictions. The MME is the terminationpoint in the network for ciphering/integrity protection for NASsignaling and handles the security key management. Lawful interceptionof signaling is also supported by the MME. The MME also provides thecontrol plane function for mobility between LTE and 2G/3G accessnetworks with the S3 interface terminating at the MME from the SGSN (notshown). The MME also terminates the S6a interface towards the home HSSfor roaming UEs.

The ePDG 122 is responsible for interworking between the EPC and fixednon-3GPP access technologies such as a WiFi, WiMAX, LTE metro, andfemtocell access networks. The ePDG 122 can use IPSec/IKEv2 to providesecure access to the EPC network. Optionally, the ePDG can use ProxyMobile IPv6 (PMIPv6) to interact with the PGW when the mobile subscriberis roaming in an untrusted non-3GPP system. The ePDG is involved intunnel authentication and authorization, transport level packet markingin the uplink, policy enforcement of Quality of Service (QoS) based oninformation received via Authorization, Authentication, Accounting (AAA)infrastructure, lawful interception, and other functions.

FIG. 2 illustrates a communication network that implements a dynamicload management mechanism with legacy universal mobiletelecommunications systems (UMTS) network devices in accordance withcertain embodiments. The legacy transceivers include base transceiverstation (BTS) 200 and NodeB transceiver 202. The BTS 200 can communicatewith a GSM EDGE Radio Access Network (GERAN) 204 and the NodeB 202 cancommunicate with a UMTS terrestrial radio access network (UTRAN) 206.The serving GPRS support node (SGSN) can be implemented on a gateway 208with a mobility management entity (MME). The GERAN 204 can communicatethrough the SGSN functionality on gateway 208 to serving gateway (SGW)212 or gateway GPRS support node (GGSN)/PGW 214.

In some embodiments, the distributed dynamic load management scheme canbe implemented on access gateways that provide network access to mobilestations, such as SGSN/MME 208, PGW/GGSN 214, and IMS 128. The accessgateway can access and maintain information relating to thecommunication session, the subscriber, the radio bearers, and thepolicies relating to the communication session. The access gateway maybe used to provide various services to a mobile device and implement thequality of service (QoS) on packet flows. Several of these functions areused in providing, for example, voice over IP (VoIP) routing andenhanced services, such as enhanced charging, stateful firewalls,traffic performance optimization (TPO). The communication networks alsoallow provision of applications such as VoIP, streaming video, streamingmusic, multi-user gaming, location based services, and a variety ofcontent delivered to a mobile node. Residing within the gateway can beone or more network processing units, line cards, as well as packet andvoice processing cards.

Network devices can share their real-time load information to enabledistributed load management. A network device can track its own loadinformation in real-time, therefore each network device can make localdecisions in response to its real-time load. For example, each networkdevice can autonomously diagnose whether the network device is in anoverloaded state, and if so, it can notify the operator for furtherinstructions. Conventionally, a network device is not aware of thereal-time load information at other network devices, so each networkdevice can only make informed decisions for itself. However, if eachnetwork device shares its load information with every other networkdevices, each network device can become aware of the network-wide loadinformation and can make informed decision involving other networkdevices as well as itself.

A network device can share its real-time load information with othernetwork devices by establishing inter-device communication channels. Thereal-time load information for a network device can include one or moreof the following: (1) the number of mobile stations currently attachedto the network device, (2) the number of additional mobile stations thatcan be attached to the network device, (3) the amount of data currentlybeing handled by the network device, and (4) the amount of additionaldata that can be handled by the network device. A network device canalso communicate control data and user data as well as load informationover the communication channel. Using the inter-device communicationchannels, a network device can share one or more of the following: (1)the maximum amount of load that can be handled by the device, (2) anetwork device identifier, such as the network resource identifier (NRI)of the device, (3) data transfer capacity (i.e., the amount of data thatcan be handled, also known as data transfer bandwidth, or the number ofmobile stations that can be handled) that can be set aside for othernetwork devices, (4) session information, for instance contextinformation, of mobile stations attached to the network device, and (5)buffered data for mobile stations attached to the device. Using theinformation shared on the inter-device communication channels, eachnetwork device can determine whether any data traffic can be handed overto other network devices, and if so, how much data traffic can be handedover to other network devices. A network device that hands over its datatraffic to other network devices is called a source device; a networkdevice that receives the data traffic is called a target device. Oncethe source device decides to hand over some of its data traffic totarget devices, the source device can transmit session information aswell as buffered data associated with the handed-over data traffic tothe target devices using the inter-device communication channels. Thisenables a data traffic hand over with little or no data loss.

The inter-device communication channels can directly couple every pairof network devices, or they can couple network devices in a serialmanner (e.g. a ring topology) where each network device is connected totwo other network devices to form a ring. The disclosed systems andmethods are not bound by a particular topology of the inter-devicecommunication channels. The disclosed systems and methods are also notbound by a communication protocol used in the inter-device communicationchannels. Furthermore, the disclosed systems and methods are not boundby a particular communication medium; for instance, the inter-devicecommunication channel can be established on a physical link, a wirelesslink, or a network.

The benefit of using inter-device communication channels is illustratedin detail using two example embodiments: network device overloadprevention and network device offloading.

Network Device Overload Prevention

In accordance with certain embodiments, the distributed dynamic loadmanagement scheme can prevent network device overloading. FIG. 3illustrates an example embodiment of a pooled network. This exampleembodiment includes three access gateways 250A-250C, connected usinginter-device communication channels 268. All access gateways areconnected to an anchor gateway 256 to access external network. In thisembodiment, a mobile station 262A-262C accessing the GPRS network isconsidered. Therefore, the access gateway 250A-250C is a Service GPRSSupport Node (SGSN) and the anchor gateway 256 is a Gateway GPRS SupportNode (GGSN). Each SGSN 250A-250C is also connected to every RadioNetwork Controller (RNC) 258 and/or Base Station Controller (BSC) 260through a radio access network, such as UMTS Terrestrial Radio AccessNetwork (UTRAN) 264 and GSM EDGE Radio Access Network (GERAN) 266. EachSGSN 250A-250C can request RNC 258/BSC 260 to re-route a mobile station262A-262C to another SGSN 250A-250C by modifying a serving networkdevice identifier in a mobile station identifier associated with themobile station 262. A serving network device identifier can include anetwork resource identifier (NRI), and a mobile station identifier caninclude Temporary Mobile Subscriber Identity (TMSI) and Packet-TemporaryMobile Subscriber Identity (P-TMSI).

In this network embodiment, access gateway-1 250A (source SGSN) isreaching its load capacity. Without the overload prevention capability,the source SGSN 250A would simply turn down any new attach requests frommobile stations. However, using the distributed dynamic load managementscheme, the network can reconfigure itself according to the real-timeload so that more mobile stations can be accommodated. To do so, beforethe source SGSN 250A becomes overloaded, the source SGSN 250A can notifyother SGSNs 250B/250C (target SGSNs) using the inter-devicecommunication channels 268 that the source SGSN 250A may overload. Inaddition to notifying the overload condition, the source SGSN 250A canalso query which target SGSNs 250B/250C can accommodate more load sothat, in case the source SGSN 250A receives a new attach request from amobile station 262A-262C, the source SGSN 250A can hand over the newattach request to target SGSNs 250B/250C. Essentially, the source SGSN250A prepares its response to new attach requests based on the loadinformation at target SGSNs 250B/250C. When the source SGSN 250A doesreceive new attach requests from mobile stations, the source SGSN 250Acan hand over those attach requests to under-utilized target SGSNs250B/250C. Therefore, the dynamic load management improves the networkefficiency by fully utilizing available resources. It can lead tosubscriber satisfaction and prevent revenue losses for operators byserving more data requests.

FIG. 4 shows a detailed flow diagram of the overloading preventionmechanism in accordance with certain embodiments. Before any of thesesteps are carried out, the inter-device communication channels 268 areestablished. As described above, the source SGSN 250A is close toreaching its load capacity. This condition can be detected manually bythe network operator or automatically by the source SGSN 250A byinspecting its own data load. In step 1, the source SGSN 250A can sendan inquiry message, which can include SGSN Load Query, to target SGSNs250B/250C to broadcast that the source SGSN 250A is about to overflowand to query target SGSNs' real-time load information. In this step, thesource SGSN 250A can also send a request message to request target SGSNsto set aside data transfer capacity for the source SGSN 250A. In step 2,target SGSNs 250B/250C can respond to the inquiry message and therequest message. In their response, target SGSNs 250B/250C can indicateone or more of the following: (1) the amount of real-time data load, (2)how many new subscribers they can accommodate and for how long thisinformation is valid, (3) whether they can reserve their data transfercapacity for the source SGSN 250A, and (4) their Network ResourceIdentifier (NRI), which can be used for re-routing new attach requestsfrom the source SGSN 250A. In order to reduce the inter-devicecommunication overhead, steps 1-2 can be performed only once when theamount of data load at the source SGSN 250A is reaching its maximum datatransfer capacity.

In step 3, a new mobile station (MS) 262 sends an attach request to thesource SGSN 250A and requests a Routing Area Update (RAU). The sourceSGSN 250A carries out the attach procedure and authenticates the MS 262.In step 4, upon authentication, the source SGSN 250A accepts the attachrequest and the RAU request, but with a Packet-Temporary MobileSubscriber Identity (P-TMSI) carrying the NRI of the target SGSN250B/250C, the Routing Area Identification (RAI) of the source SGSN250A, and a timer value. The timer value can be a routing area updateperiodic timer value that indicates whether the update is stale. It caninclude a low periodic RAU timer value, typically 4 ms, but can be lessthan or greater than this value. In step 5, once the MS 262 receives themessage that the RAU request has been accepted, it sends a RAU Completeflag to the source SGSN 250A to indicate that the connection isestablished.

In step 6, soon after sending the RAU Complete flag, the MS 262 sendsanother RAU request. This time, the request is sent to one of the targetSGSNs 250B/250C, specified by the modified NRI stored in P-TMSI. Thetarget SGSN 250B/250C performs a security check, and once the securitycheck is successful, in step 7, the target SGSN 250B/250C sends asession information (i.e., context information) request to the sourceSGSN 250A. In step 8, the source SGSN 250A responds to the sessioninformation request with the MS's session information, and in step 9,the target SGSN 250B/250C acknowledges it. Subsequently, in step 10, thetarget SGSN 250B/250C requests GGSN 256 to update the Packet DataProtocol (PDP) contexts, and GGSN 256 acknowledges it. In step 11, thetarget SGSN 250B/250C requests the Home Location Register (HLR) 270 toupdate the GPRS location. In steps 12-13, the HLR 270 communicates withthe source SGSN 250A to cancel the stored location on the source SGSN250A, and the HLR 270 sends a message to the target SGSN 250B/250C toacknowledge that the GPRS location has been updated. Once theseoperations are successfully carried out, the target SGSN 250B/250C andthe MS 262 complete the routing area update.

The source SGSN 250A repeats steps 4-15 for every new attach request(step 3) until the source SGSN 250A is no longer close to overloading.When the source SGSN 250A can accommodate new attach requests frommobile stations, the source SGSN 250A can notify target SGSNs 250B/250Cto release the data transfer capacity reserved for the source SGSN 250A.

Network Device Offloading

In some embodiments, a network device offloads a large amount of load toother network devices. This can be useful when network devices are takenoff-line for maintenance purposes. Offloading mobile stations can beespecially challenging when the selected network devices are activelyserving those mobile stations, in which case offloading can lead toservice disruptions. Even in this challenging scenario, however, theinter-device load communication enables offloading data traffic from thesource network device to target network devices with little or noservice disruption.

In accordance with certain embodiments, the distributed dynamic loadmanagement scheme can help offload a large amount of data traffic fromnetwork devices. FIG. 5 illustrates an example embodiment in which theoperator decides to stop the operation of the access gateway-1 250A(source device). In this embodiment, a mobile station accessing the GPRSnetwork is illustrated. Therefore, the access gateway 250A-250C is aService GPRS Support Node (SGSN) and the anchor gateway 256 is a GatewayGPRS Support Note (GGSN). Using the inter-device communication scheme,the source SGSN 250A can notify target SGSNs 250B/250C of impendingoffloading and query which target SGSNs 250B/250C can accommodate moredata traffic. The source SGSN 250A can inspect target SGSNs' responsesto determine how much of its data load can be handed over to each targetSGSN 250B/250C. Given this information, the source SGSN 250A can handover MS sessions to target SGSNs 250B/250C, and instruct an RNC/BSC258/260 to re-route the selected MS 262 to each target SGSN 250B/250C.This offloading scheme can distribute the data load to fully utilizenetwork resources without overloading other network devices. It can alsobe fully automatic, ensuring fast and efficient offloading operations.In addition, this scheme can be used in conjunction with standardoffloading procedures, including Iu flex or Gb flex described in 3GPP TS23. 236., without altering them, therefore this scheme can betransparent to other devices in the network, such as RNC 260 or BSC 258.

FIG. 6 illustrates a detailed flow diagram of the distributed, dynamicload aware offloading in accordance with certain embodiments. Asdescribed above, the operator decides to offload the source SGSN 250A.The offload procedure starts with the source SGSN 250A communicatingwith target SGSNs 250B/250C over the inter-device communication channel.In steps 1-7, the source SGSN 250A determines the amount of load to handover to each target SGSN 250B/250C. In this process, the source SGSN250A can negotiate with each target SGSN 250B/250C the amount of load tobe handed over from the source SGSN 250A. In step 1, the source SGSN250A can send an inquiry message, which includes SGSN Load Query, totarget SGSNs 250B/250C to query target SGSNs' real-time loadinformation. In step 2, each target SGSN 250B/250C can respond to thesource SGSN 250A's inquiry message indicating the target SGSN'sreal-time load information, which can include whether or not the targetSGSN 250B/250C can accommodate more data load. If the target SGSN250B/250C can accommodate more data load, it can reserve some of itsdata transfer capacity for the source SGSN 250A, and indicate in theresponse to the source SGSN 250A the amount of extra data load it canaccommodate. Each target SGSN 250B/250C can autonomously make thisdecision based on its real-time load information.

In steps 3-4, once the source SGSN 250A receives responses from targetSGSNs 250B/250C, the source SGSN 250A can determine the amount of loadto hand over to each of the target SGSNs 250B/250C. Then the source SGSN250A can send a request message, which can include a SGSN OffloadRequest, to available target SGSNs 250B/250C to request setting asidedata transfer capacity for the source SGSN 250A. In this requestmessage, source SGSN 250A can include International Mobile SubscriberIdentity (IMSI), Mobility Management (MM) context, and Packet DataProtocol (PDP) contexts of one or more MSs 262 that will be handed overto the target SGSNs 250B/250C. After sending the request, the sourceSGSN 250A immediately starts a timer “t1” to guard against potentialerror in the offloading process. In steps 5-6, upon receiving theoffload request from the source SGSN 250A, each target SGSN 250B/250Caccepts the request by responding with a message. This message caninclude a set of P-TMSI and Tunnel Endpoint Identifier (TEID) that canbe used to hand over mobile stations to the target SGSN 250B/250C. Inthe above steps, messages can include information for one or more MSs262, depending on the GTP control messaging scheme. This optimizationcan reduce the amount of communicated data between SGSNs 250A-250C.After responding to the offload request, each target SGSN 250B/250Cstarts a guard timer “t2” immediately. In step 7, the source SGSN 250Acan acknowledge the message from the target SGSN 250B/250C. In theacknowledgement message in step 7, the source SGSN 250A can confirm thatit will only offload previously negotiated amount of load to each targetSGSN 250B/250C.

At this point, the source SGSN 250A has sufficient information tooffload mobile stations in a controlled manner. The source SGSN 250A nowselects mobile stations that will be handed over to each target SGSN250B/250C, and initiates offloading procedures. In step 8, the sourceSGSN 250A sends a P-TMSI reallocation command to the radio accessnetwork, which relays the information to the corresponding MS 262. TheP-TMSI reallocation command contains the P-TMSI received from the targetSGSNs 250B/250C. The P-TMSI in the P-TMSI reallocation command containsa serving network device identifier indicating that the MS should bere-routed to the target SGSNs 250B/250C. This step ensures thatoffloaded data traffic will not land back on the source SGSN 250A. IfSGSNs 250A-250C are operating in a 2G network, a “force to standby” bitcan be set. In step 9, the MSs can change their P-TMSI and send a flagto the source SGSN 250A to acknowledge the change of their P-TMSI. Step10 is only applicable for SGSNs 250A-250C operating in a 3G network. Inthis step, the source SGSN 250A initiates Iu release procedures with aBSC/RNC 258/260. In step 11, the source SGSN 250A communicates with thetarget SGSNs 250B/250C to confirm the offloading, and in step 12 targetSGSNs 250B/250C acknowledge the offload confirmation.

While these offloading procedures are carried out, the core network cancontinue to send data to the MSs 262. The data can include voice data,video data, and text data. If the source SGSN 250A receives data thatshould be delivered to the re-routed MSs 262, the source SGSN 250A cantemporarily store the received data in a link buffer. In step 11, inaddition to the offloading confirmation, the source SGSN 250A can sendthe buffered data to the corresponding target SGSNs 250B/250C using theinter-device communication channels so that the target SGSNs 250B/250Ccan relay the buffered data to the re-routed MSs 262. This datahand-over operation ensures that the data packets for the re-routed MSs262 are not lost during the offloading procedures, even if the sourceSGSN 250A was actively serving the re-routed MSs 262. Therefore, thedata hand-over operation prevents session disruptions and ensuressession continuity.

In steps 13-14, each target SGSN 250B/250C communicates with the GGSN256 to update the PDP contexts. This operation notifies the GGSN 256that the target SGSN 250B/250C is now serving the MS 262. Upon receivingthis request, the GGSN 256 can update the PDP contexts and the GGSN 256may also transmit data for the MS 262 to the target SGSN 250B/250C,which would be placed in target SGSN's buffer. If the MS 262 has not yetinitiated signaling its new SGSN (i.e., target SGSN) by sending, forinstance, Initial UE or Logical Link Control (LLC) frame, the targetSGSN 250B/250C may send a paging request to the MS 262 in step 15. Bythis point, the target SGSN 250B/250C is ready to handle any Initial UEmessage (e.g. Attach, RAU, Service request, Detach) from the new P-TMSI.If the target SGSN 250B/250C operates on a 2G network, it is ready tohandle any LLC frame with new Temporary Logical Link Identifier (TLLI).In step 16, the target SGSN 250B/250C can accommodate a signalinitiation or a paging response from newly assigned MSs 262.

In steps 17-20, upon receiving a signal initiation or a paging responsefrom the MS 262, the target SGSN 250B/250C stops the guard timer “t2”,and sends an offload-complete message to the source SGSN 250A toindicate that the offloading is complete. Upon receiving theoffload-complete message, the source SGSN 250A can stop the guard timer“t1”. If the offload-complete message is not received before the guardtimer “t1” reaches a preselected threshold value, the source SGSN 250Acan send an error message to the network operator, and optionally stopthe offload procedures and roll-back any operations performed since thestart of the guard timer “t1”. If the source SGSN 250A has received aCancel-Location request, it can also clean up the MM context and/or PDPcontexts. The target SGSN 250B/250C can process the signal initiation orthe paging response from the MS 262 and perform security functions,which may involve communicating with the HLR 270 and with the MS 262.

In steps 21-24, as part of the paging response processing procedure, thetarget SGSN 250B/250C can request the HLR 270 to update the GPRSlocation. In response to the target SGSN's request, the HLR 270 canrequest the source SGSN 250A to cancel the location. the source SGSN250A can acknowledge the Cancel Location request to the HLR 270. If theguard timer “t2” is not running, the source SGSN 250A can clean up theMM context and/or the PDP contexts; otherwise the source SGSN 250A canwait until the timer “t2” expires. The HLR 270 then sends a GPRSlocation update acknowledgment to the target SGSN 250B/250C. In step 25,the target SGSN 250B/250C can send Paging_response_procedure_accept tothe MS 262. This step may not be carried out if the service request wasa paging response or a signal indication from the MS 262. Uponcompleting the offloading procedure, the target SGSN 250B/250C can sendany buffered data to the MS 262. This ensures that the offloadingprocedure is transparent to MSs 262.

Once the offloading is complete, the network can operate in a normalmode with the reduced number of operating network devices. When thesource SGSN 250A is back on service and is ready to take on MSconnections, the source SGSN 250A can send a return message to targetSGSNs 250B/250C to request returning all MS connections offloaded fromthe source SGSN 250A to the source SGSN 250A.

The offloading scheme in FIG. 6 can be modified to proactively balanceload across SGSNs. One possible modification is to let every SGSN250A-250C communicate its real-time load information to every otherSGSNs 250A-250C at a constant time interval. Based on the amount of dataload on other SGSNs 250A-250C, each SGSN 250A-250C can decide to offloada certain amount of data traffic to under-utilized network devices. Forinstance, if the amount of load on a source SGSN 250A is greater thanthe amount of load at a target SGSN 250B/250C by a pre-determined amountor a threshold, then the source SGSN 250A can initiate the offloadingprocedures in steps 3-25 of FIG. 6. In an example embodiment ofproactive load balancing, every SGSN 250A-250C would communicate withevery other SGSNs 250A-250C to notify its real-time load at a constanttime interval. In other words, instead of steps 1-2 of FIG. 6, in whichthe source SGSN 250A has to query for the real-time load information,every SGSN 250A-250C can receive the real-time load information of everyother SGSNs 250A-250C without querying. And once one of the SGSNs (i.e.,source SGSN) determines that it is carrying a larger amount of loadcompared to another SGSN (i.e., target SGSN) by a pre-determinedthreshold, the source SGSN 250A can initiate the offload procedures(i.e. steps 3-25) to offload MS sessions to the target SGSN 250B/250C.This scheme can balance the load distribution across SGSNs in thenetwork.

FIG. 7 illustrates a logical view of a network device 300 in accordancewith certain embodiments. The network device 300 includes a networkprocessing unit (NPU) 322, a packet director/NPU flow 302, a channelmodule 304, a session 306, a session manager 308, interfaces 310, aprocess 312, a session cache/database 314, a task 316, a memory 318, aprocessor 320, a link buffer 324, and a load module 326.

Interfaces 310 can provide an input and/or output mechanism tocommunicate with other network devices. Interfaces can allowcommunication with mobile stations, domain name servers, as well asother gateways to send and receive data in the network. In particular,an offload interface, which is one of the Interfaces 310, can provideinter-device communication channels. Interfaces can be implemented inhardware to send and receive signals in a variety of mediums, such asoptical, copper, and wireless and in a number of different protocolssome of which may be non-transient.

A channel module 304 can establish inter-device communication channelswith other network devices. The channel module 304 can also manage datacommunication over the inter-device communication channels in accordancewith a communication medium or a protocol. A load module 326 can measurethe real-time load at the network device 300. The load module 326 canmonitor one or more of the interfaces 310, the processor 320, and thechannel module 304 to measure the amount of load carried by the networkdevice 300. When the network device 300 has sufficient information foroffloading, it selects mobile stations to be handed over to each targetnetwork device using a selection module. A processor 320 can hand overthe selected mobile stations by modifying a serving network deviceidentifier in a mobile station identifier. The modules can beimplemented in software using memory 318 such as a computer readablemedium, a programmable read only memory (PROM), or flash memory. Thesoftware can run on a processor 320 that executes instructions orcomputer code. The modules may also be implemented in hardware using anapplication specific integrated circuit (ASIC), programmable logic array(PLA), or any other integrated circuit.

A link buffer 324 can temporarily store data received for the mobilestations that have been rerouted to other network devices. The data inthe link buffer can be transmitted to target network devices that carrythe re-routed mobile stations using the inter-device communicationchannels. The transmission of the data stored in the link buffer 324 canbe scheduled by the channel manager 304. A link buffer can beimplemented using memory 318 such as a computer readable medium, aprogrammable read only memory (PROM), or flash memory.

A session manager 308 can provide management of a session 306 on thenetwork device. A session 306 can include one or more connections for asubscriber in the service provider's network. A session 306 can includeinformation relating to the mobile device or mobile station as well asto each data connection established with the mobile station over thenetwork. The session can include policy information, billinginformation, services to be provided, quality of service (QoS)information, and any other applicable information. Each session 306 canshare the processor 320 and memory 318 resources on the network device.The session manager 308 can work with other modules and components inthe network device to ensure the session is handled appropriately. Thesession manager 308 can assign resources, perform tasks, and loginformation regarding the session.

Mobile Station and Gateway

The mobile station described above can communicate with a plurality ofradio access networks using a plurality of access technologies and withwired communication networks. The mobile station can be a smart phoneoffering advanced capabilities such as word processing, web browsing,gaming, e-book capabilities, an operating system, and a full keyboard.The mobile station may run an operating system such as Symbian OS,iPhone OS, RIM's Blackberry, Windows Mobile, Linux, Palm WebOS, andAndroid. The screen may be a touch screen that can be used to input datato the mobile device and the screen can be used instead of the fullkeyboard. The mobile station may have the capability to run applicationsor communicate with applications that are provided by servers in thecommunication network. The mobile station can receive updates and otherinformation from these applications on the network.

The mobile station also encompasses many other devices such astelevisions (TVs), video projectors, set-top boxes or set-top units,digital video recorders (DVR), computers, netbooks, laptops, and anyother audio/visual equipment that can communicate with a network. Themobile station can also keep global positioning coordinates, profileinformation, or other location information in its stack or memory. Themobile station can have a memory such as a computer readable medium,flash memory, a magnetic disk drive, an optical drive, a programmableread-only memory (PROM), and/or a read-only memory (ROM). The mobilestation can be configured with one or more processors that processinstructions and run software that may be stored in memory. Theprocessor can also communicate with the memory and interfaces tocommunicate with other devices. The processor can be any applicableprocessor such as a system-on-a-chip that combines a CPU, an applicationprocessor, and flash memory. The interfaces can be implemented inhardware or software. The interfaces can be used to receive both dataand control information from the network as well as local sources, suchas a remote control to a television. The mobile station can also providea variety of user interfaces such as a keyboard, a touch screen, atrackball, a touch pad, and/or a mouse. The mobile station may alsoinclude speakers and a display device in some embodiments.

The distributed dynamic load management described above is implementedin a network device in some embodiments. This network device canimplement multiple and different integrated functionalities. In someembodiments, one or more of the following functionalities can beimplemented on the network device including a security gateway (SeGW),an access gateway, a Gateway General packet radio service Serving Node(GGSN), a serving GPRS support node (SGSN), a packet data inter-workingfunction (PDIF), an access service network gateway (ASNGW), a User PlaneEntity (UPE), an IP Gateway, a session initiation protocol (SIP) server,a proxy-call session control function (P-CSCF), and aninterrogating-call session control function (I-CSCF), a serving gateway(SGW), and a packet data network gateway (PDN GW), a mobility managemententity (MME), a mobility access gateway (MAG), an HRPD serving gateway(HSGW), a local mobility anchor (LMA), a packet data serving node(PDSN), a foreign agent (FA), and/or home agent (HA). The distributeddynamic load management can be implemented on network devices of thesame type, implementing the same set of functionalities.

In certain embodiments, the functionalities are provided by acombination of hardware and software in the network device. Generalpurpose hardware can be configured in the network device to provide oneor more of these specialized functionalities. The gateway can alsosupport sessions originated from a Femto base station, which wouldconnect to the gateway using a broadband network. A person orcorporation may use a Femto base station in a home or business tosupport one or more mobile nodes. The gateway can provide trigger basedtraffic management during a handoff from a Femto base station to a macrobase station, while maintain traffic management for the mobile node. Theoffload gateway can be implemented as any combination of the followingincluding an xGSN, an xGW, an xGW-SGW, and an xGW-PGW.

In some embodiments the network device is implemented using a collectionof integrated circuit boards or cards. These cards include input/outputinterfaces for communication amongst each other, at least one processorfor executing instructions and running modules that are stored inmemory, and memory for storing data. The features of a network devicethat implements a gateway, in accordance with some embodiments, arefurther described below. FIG. 8 illustrates the implementation of anetwork device in accordance with some embodiments. The network device400 includes slots 402 for loading application cards and line cards. Amidplane can be used in the network device to provide intra-networkdevice communications, power connections, and transport paths betweenthe various installed cards. The midplane can include buses such as aswitch fabric 404, a control bus 406, a system management bus, aredundancy bus 408, and a time division multiplex (TDM) bus. The switchfabric 404 is an IP-based transport path for user data throughout thenetwork device implemented by establishing inter-card communicationsbetween application cards and line cards. The control bus 406interconnects the control and management processors within the networkdevice. The network device management bus provides management of systemfunctions such as supplying power, monitoring temperatures, boardstatus, data path errors, card resets, and other failover features. Theredundancy bus 408 provides transportation of user data and redundancylinks in the event of hardware failures. The TDM bus provides supportfor voice services on the system.

The network device supports at least four types of application cards: aswitch processor I/O card (SPIO) 410, a system management card (SMC)412, a packet service card (PSC) 414, and a packet accelerator card (notshown). Other cards used in the network device include line cards 466and redundant crossbar cards (RCC) 418. The line cards 416, when loadedin the network device, provide input/output connectivity to the networkand other devices, as well as redundancy connections. The line cards 416include interfaces to the network through Ethernet, Fiber Optic, and theother communication mediums. The redundant crossbar card (RCC) 418includes a non-blocking crossbar and connections to each of the cards inthe network device. This allows a redundant connection to be madethrough the redundant crossbar card 418 from any one card to any othercard in the network device. The SPIO card 410 serves as a controller ofthe network device and is responsible for such things as initializingthe network device and loading software configurations onto other cardsin the network device.

The system management card (SMC) 412 and switch processor card (notshown) are system control and management cards for managing andcontrolling other cards in the network device. The packet acceleratorcard (PAC) and packet service card (PSC) 414 provide packet processing,context processing capabilities, and forwarding capabilities among otherthings. The PAC and PSC 414 perform packet-processing operations throughthe use of control processors and a network processing unit. The networkprocessing unit determines packet processing requirements; receives andtransmits user data frames to/from various physical interfaces; makes IPforwarding decisions; implements packet filtering, flow insertion,deletion, and modification; performs traffic management and trafficengineering; modifies/adds/strips packet headers; and manages line cardports and internal packet transportation. The control processors, alsolocated on the packet accelerator card, provide packet-based userservice processing.

The operating system software can be based on a Linux software kerneland run specific applications in the network device such as monitoringtasks and providing protocol stacks. The software allows network deviceresources to be allocated separately for control and data paths. Forexample, certain packet accelerator cards and packet services cards canbe dedicated to performing routing or security control functions, whileother packet accelerator cards/packet services cards are dedicated toprocessing user session traffic. As network requirements change,hardware resources can be dynamically deployed to meet the requirementsin some embodiments. The system can be virtualized to support multiplelogical instances of services, such as technology functions (e.g., aSeGW PGW, SGW, MME, HSGW, PDSN, ASNGW, PDIF, HA, or GGSN).

The network device's software can be divided into a series of tasks thatperform specific functions. These tasks communicate with each other asneeded to share control and data information throughout the networkdevice. A task is a software process that performs a specific functionrelated to system control or session processing. Three types of tasksoperate within the network device in some embodiments: critical tasks,controller tasks, and manager tasks. The critical tasks controlfunctions that relate to the network device's ability to process callssuch as network device initialization, error detection, and recoverytasks. The controller tasks mask the distributed nature of the softwarefrom the user and perform tasks such as monitor the state of subordinatemanager(s), provide for intra-manager communication within the samesubsystem, and enable inter-subsystem communication by communicatingwith controller(s) belonging to other subsystems. The manager tasks cancontrol system resources and maintain logical mappings between systemresources.

Individual tasks that run on processors in the application cards can bedivided into subsystems. A subsystem is a software element that eitherperforms a specific task or is a culmination of multiple other tasks. Asingle subsystem can include critical tasks, controller tasks, andmanager tasks. Some of the subsystems that can run on a network deviceinclude a system initiation task subsystem, a high availability tasksubsystem, a recovery control task subsystem, a shared configurationtask subsystem, a resource management subsystem, a virtual privatenetwork subsystem, a network processing unit subsystem, a card/slot/portsubsystem, and a session subsystem.

The system initiation task subsystem is responsible for starting a setof initial tasks at system startup and providing individual tasks asneeded. The high availability task subsystem works in conjunction withthe recovery control task subsystem to maintain the operational state ofthe network device by monitoring the various software and hardwarecomponents of the network device. Recovery control task subsystem isresponsible for executing a recovery action for failures that occur inthe network device and receives recovery actions from the highavailability task subsystem. Processing tasks are distributed intomultiple instances running in parallel so if an unrecoverable softwarefault occurs, the entire processing capabilities for that task are notlost. User session processes can be sub-grouped into collections ofsessions so that if a problem is encountered in one sub-group users inanother sub-group will not be affected by that problem.

The architecture also allows check-pointing of processes, which is amechanism to protect the system against any critical software processesthat may fail. The self-healing attributes of the software architectureprotects the system by anticipating failures and instantly spawningmirror processes locally or across card boundaries to continue theoperation with little or no disruption of service. This uniquearchitecture allows the system to perform at the highest level ofresiliency and protects the user's data sessions while ensuring completeaccounting data integrity.

Shared configuration task subsystem provides the network device with anability to set, retrieve, and receive notification of network deviceconfiguration parameter changes and is responsible for storingconfiguration data for the applications running within the networkdevice. A resource management subsystem is responsible for assigningresources (e.g., processor and memory capabilities) to tasks and formonitoring the task's use of the resources.

Virtual private network (VPN) subsystem manages the administrative andoperational aspects of VPN-related entities in the network device, whichinclude creating separate VPN contexts, starting IP services within aVPN context, managing IP pools and subscriber IP addresses, anddistributing the IP flow information within a VPN context. In someembodiments, within the network device, IP operations are done withinspecific VPN contexts. The network processing unit subsystem isresponsible for many of the functions listed above for the networkprocessing unit. The card/slot/port subsystem is responsible forcoordinating the events that occur relating to card activity such asdiscovery and configuration of ports on newly inserted cards anddetermining how line cards map to application cards.

The session subsystem is responsible for processing and monitoring amobile subscriber's data flows in some embodiments. Session processingtasks for mobile data communications include: S1/S5/S8 interfacetermination for LTE networks, A10/A11 interface termination for CDMAnetworks, GSM tunneling protocol (GTP) termination for GPRS and/or UMTSnetworks, asynchronous PPP processing, IPsec, packet filtering, packetscheduling, Diffsery codepoint marking, statistics gathering, IPforwarding, and AAA services, for example. Responsibility for each ofthese items can be distributed across subordinate tasks (calledmanagers) to provide for more efficient processing and greaterredundancy. A separate session controller task serves as an integratedcontrol node to regulate and monitor the managers and to communicatewith the other active subsystem. The session subsystem also managesspecialized user data processing such as payload transformation,filtering, statistics collection, policing, and scheduling.

In providing emulation, as MIPv4 is received from a mobile node, thesession subsystem can setup a MIPv4 termination and setup a PMIPv6session towards the core network. A session manager can track themapping of the sessions and processing to provide the emulation andinter-working between the networks. A database can also be used to mapinformation between the sessions, and store, for example, NAI, HoA, AEinformation in some embodiments.

The network device allows system resources to be allocated separatelyfor control and data paths. For example, certain PACs/PSCs could bededicated to performing routing or security control functions whileother PACs/PSCs are dedicated to processing user session traffic. Asnetwork requirements grow and call models change, hardware resources canbe added to accommodate processes, such as encryption, packet filtering,etc., that require more processing power. FIG. 9 illustrates a logicalview of the software architecture of a network device in accordance withcertain embodiments. As shown, the software and hardware can bedistributed within the network device and across different circuitboards, processors, and memory. FIG. 9 includes a primary switchprocessor card (SPC)/system management card (SMC) 500 a, a secondarySPC/SMC 500 b, PAC/PSC 502 a-502 d, a communication path 504, and asynchronization path 506. The SPC/SMC 500 include a memory 508, aprocessor 510, a boot configuration 512, high availability tasks 514,resource manager 516, switch fabric control 518, and controller tasks520.

The SPC/SMC 500 manage and control the network device including theother cards in the network device. The SPC/SMC 500 can be configured ina primary and secondary arrangement that provides redundancy andfailsafe protection. The modules or tasks running on the SPC/SMC 500 arerelated to network device wide control and management. The bootconfiguration task 512 includes information for starting up and testingthe network device. The network device can also be configured to startupin different configurations and providing different implementations.These can include which functionalities and services are capable ofrunning on the SPC/SMC 500. The high availability task 514 maintains theoperational state of the network device by monitoring the device andmanaging recovery efforts to avoid disruption of service. The resourcemanager tracks and assigns the available resources for sessions anddemands on the network device. This can include load balancing amongdifferent processors and tasks running on the network device. Processescan be distributed across the system to fit the needs of the networkmodel and specific process requirements. For example, most tasks can beconfigured to execute on SPC/SMC 500 or a PAC/PSC 502, while someprocessor intensive tasks can also be performed across multiplePACs/PSCs to utilize multiple CPU resources. Distribution of these tasksis invisible to the user. The switch fabric control 518 controls thecommunication paths in the network device. The controller tasks module520 can manage the tasks among the resources of the networks to provide,for example, VPN services, assign ports, and create, delete, and modifysessions for user equipment.

The PAC/PSC 502 are high-speed processing cards that are designed forpacket processing and the tasks involved with providing various networkfunctionalities on the network device. The PAC/PSC 502 include a memory524, a network processing unit (NPU) 526, a processor 528, a hardwareengine 530, an encryption component 532, a compression component 534,and a filter component 536. Hardware engines 530 can be deployed withthe card to support parallel distributed processing for compression,classification traffic scheduling, forwarding, packet filtering, andstatistics compilations. The components can provide specializeprocessing that can be done more efficiently than using a generalprocessor in some embodiments.

Each PAC/PSC 502 is capable of supporting multiple contexts. The PAC/PSC502 are also capable of running a variety of tasks or modules. PAC/PSC502 a provides routing managers 522 with each covering routing of adifferent domain. PAC/PSC 502 b provides a session manager 538 and anAAA manager 540. The session manager 538 manages one or more sessionsthat correspond to one or more user equipment. A session allows a mobilestation to communicate with the network for voice calls and data. TheAAA manager 540 manages accounting, authentication, and authorizationwith an AAA server in the network. PAC/PSC 502 provides a deep packetinspection task 542 and a signaling demux 544. The deep packetinspection task 542 provides inspection of packet information beyondlayer 4 for use and analysis by the network device. The signaling demux544 can provide scalability of services in combination with othermodules. PAC/PSC 502 d provides redundancy through standby tasks 546.Standby tasks 546 store state information and other task information sothat the standby task can immediately replace an active task if a cardfails or if there is a scheduled event to remove a card.

In some embodiments, the software needed for implementing a process or adatabase includes a high level procedural or an object-orientatedlanguage such as C, C++, C#, Java, or Perl. The software may also beimplemented in assembly language if desired. Packet processingimplemented in a network device can include any processing determined bythe context. For example, packet processing may involve high-level datalink control (HDLC) framing, header compression, and/or encryption. Incertain embodiments, the software is stored on a storage medium ordevice such as read-only memory (ROM), programmable-read-only memory(PROM), electrically erasable programmable-read-only memory (EEPROM),flash memory, or a magnetic disk that is readable by a general orspecial purpose-processing unit to perform the processes described inthis document. The processors can include any microprocessor (single ormultiple core), system on chip (SoC), microcontroller, digital signalprocessor (DSP), graphics processing unit (GPU), or any other integratedcircuit capable of processing instructions such as an x86microprocessor.

Although the present disclosure has been described and illustrated inthe foregoing example embodiments, it is understood that the presentdisclosure has been made only by way of example, and that numerouschanges in the details of implementation of the disclosure may be madewithout departing from the spirit and scope of the disclosure, which islimited only by the claims which follow. Other embodiments are withinthe following claims. For example, a network of GGSNs can be configuredto share real-time load information to dynamically adjust load on eachGGSN.

We claim:
 1. A first network device comprising: a processor, incommunication with one or more interfaces that are to providecommunication with a plurality of other network devices and a pluralityof mobile stations, the processor to: receive load information from theplurality of other network devices; determine, based on at least aportion of the load information, that a network device of the pluralityof other network devices is capable of setting aside data transfercapacity for the first network device; and cause a mobile station to berouted to the network device of the plurality of other network devicesby modifying a serving network device identifier in a mobile stationidentifier associated with the mobile station to cause data to becommunicated between the mobile station and the network device of theplurality of other network devices.
 2. The first network device of claim1, wherein the serving network device identifier comprises a NetworkResource Identifier (NRI).
 3. The first network device of claim 1,wherein the mobile station identifier comprises a Temporary MobileSubscriber Identity (TMSI).
 4. The first network device of claim 1,wherein the mobile station identifier comprises a Packet-TemporaryMobile Subscriber Identity (P-TMSI).
 5. The first network device ofclaim 1, wherein the network device is a Mobility Management Entity(MME).
 6. The first network device of claim 1, wherein the networkdevice is a Serving GPRS Support Node (SGSN).
 7. The first networkdevice of claim 1, the processor further to: receive a routing areaupdate (RAU) request from the mobile station; and send a response to theRAU request to the mobile station, the response comprising the modifiedserving network device identifier, the modified serving network deviceidentifier comprising a network device identifier of the network deviceof the plurality of other network devices.
 8. The first network deviceof claim 7, wherein the response to the RAU request comprises a lowperiodic RAU timer value designed to cause the mobile station to send aRAU request to the network device of the plurality of other networkdevices after a time period corresponding to the low periodic RAU timervalue.
 9. The first network device of claim 1, wherein the other networkdevices are each of the same type of network device as the first networkdevice.
 10. The first network device of claim 1, the processor furtherto receive a message from the network device of the plurality of othernetwork devices, the message comprising load information of the networkdevice and a network device identifier of the network device.
 11. Amethod comprising: receiving, at a first network device, loadinformation of a second network device; determining, by the firstnetwork device based on the load information of the second networkdevice, that the second network device is capable of setting aside datatransfer capacity for the first network device; and causing a mobilestation to be routed to the second network device by modifying, by thefirst network device, a serving network device identifier in a mobilestation identifier associated with the mobile station to cause data tobe communicated between the mobile station and the second networkdevice.
 12. The method of claim 11, wherein the first network device andthe second network device are the same type of device.
 13. The method ofclaim 12, wherein the type of device of the first network device and thesecond network device is a Mobility Management Entity (MME).
 14. Themethod of claim 12, wherein the type of device of the first networkdevice and the second network device is a Serving GPRS Support Node(SGSN).
 15. The method of claim 11, further comprising: receiving, atthe first network device, a routing area update (RAU) request from themobile station; and sending, by the first network device, a response tothe RAU request to the mobile station, the response comprising themodified serving network device identifier, the modified serving networkdevice identifier comprising a network device identifier of the secondnetwork device.
 16. At least one non-transitory computer readable mediumcomprising logic that when executed is operable to: receive, at a firstnetwork device, load information of a second network device; determine,by the first network device based on the load information of the secondnetwork device, that the second network device is capable of settingaside data transfer capacity for the first network device; and cause amobile station to be routed to the second network device by modifying,by the first network device, a serving network device identifier in amobile station identifier associated with the mobile station to causedata to be communicated between the mobile station and the secondnetwork device.
 17. The at least one medium of claim 16, wherein thefirst network device and the second network device are the same type ofdevice.
 18. The at least one medium of claim 17, wherein the type ofdevice of the first network device and the second network device is aMobility Management Entity (MME).
 19. The at least one medium of claim17, wherein the type of device of the first network device and thesecond network device is a Serving GPRS Support Node (SGSN).
 20. The atleast one medium of claim 16, the logic when executed further to:receive, at the first network device, a routing area update (RAU)request from the mobile station; and send, by the first network device,a response to the RAU request to the mobile station, the responsecomprising the modified serving network device identifier, the modifiedserving network device identifier comprising a network device identifierof the second network device.